1. Field of the Invention
The present invention relates to new benzamidine derivatives which can be orally administered to exhibit a strong anticoagulant effect by reversibly inhibiting the activated blood coagulation factor X, anticoagulants containing them as active ingredients, and agents for preventing and treating diseases caused by thrombi or emboli. These diseases include, for example, cerebrovascular disorders such as cerebral infarction, cerebral thrombosis, cerebral embolism, transient ischemic attack (TIA) and subarachnoidal hemorrhage (vasospasm); ischemic heart diseases such as acute and chronic myocardial infarction, unstable angina and coronary thrombolysis; pulmonary vascular disorders such as pulmonary infarction and pulmonary embolism; peripheral obliteration; deep vein thrombosis; disseminated intravascular coagulation syndrome; thrombus formation after an artificial blood vessel-forming operation or artificial valve substitution; re-occlusion and re-stenosis after a coronary bypass-forming operation; re-occlusion and re-stenosis after reconstructive operation for the blood circulation such as percutaneous transluminal coronary angioplasty (PTCA) or percutaneous transluminal coronary recanalization (PTCR); and thrombus formation in the course of the extracorporeal circulation.
2. Description of the Background
As the habit of life is being westernized and people of advanced ages are increasing, thrombotic and embolismic patients such as those suffering from myocardial infarction, cerebral thrombosis and peripheral thrombosis are increasing in number year by year, and the treatment of these diseases is becoming more and more important in the society. Anticoagulation treatment bears the internal treatments for the remedy and prevention of thrombosis, like thrombolytic therapy and antiplatelet therapy.
Thrombin inhibitors were developed as thrombus-formation inhibitors in the prior art. However, it has been known that since thrombin not only controls the activation of fibrinogen to form fibrin, which is the last step of the coagulation reactions, but also deeply related to the activation and aggregation of blood platelets, the inhibition of the action of thrombin causes a danger of causing hemorrhage. In addition, when thrombin inhibitors are orally administered, the bioavailability thereof is low. At present, no thrombin inhibitor which can be orally administered is available on the market.
Since the activated blood coagulation factor X is positioned at the juncture of an extrinsic coagulation cascade reaction and an intrinsic coagulation cascade reaction and in the upstream of thrombin, it is possible to inhibit the coagulation system more efficiently and specifically, than the thrombin inhibition, by factor X inhibition (THROMBOSIS RESEARCH, Vol. 19, pages 339 to 349; 1980).